The present invention relates to gas lasers, and more particularly, to an optically pumped laser having a gain medium including at least one halide gas and at least one rare-gas.
Laser systems having gain media including halide and rare-gas elements and utilizing electron beam and/or direct electrical discharge excitation are capable of providing output beams having radiation with wavelengths in the ultraviolet and/or visible spectrum. In the utilization of electron beam excitation, an electron beam is passed through a window of thin metallic foil into a cell containing a gain medium including halide and rare-gas elements, such as xenon, krypton and fluorine. The electron beam is typically passed into the cell along the length of the metal foil transverse to the optical axis. The energy deposited in the gain medium by the interaction of the electron beam with the gas molecules produces a diffuse discharge with a resulting population inversion of the energy levels of the gain medium. An optical cavity, having optical elements bounding the discharge, amplifies the radiation produced by the de-excitation of the energy levels by multiple reflections between the optical elements. A laser beam having a wavelength in the ultraviolet portion of the spectrum is typically out coupled from the cavity by transmission through one of the optical elements. A second electron beam excitation technique employs an electron beam to produce ionization within a cell of a gain medium including halide and rare-gas elements and an electrical field to maintain a diffuse electric discharge within the gain medium to supply the bulk of the input energy. In principle, the second electron beam technique is more efficient than direct electron beam pumping since the discharge conditions can be optimized more effectively.
Direct electrical excitation of a gain medium including halide and rare-gas elements with an electric field to produce a laser beam having a wavelength in the ultraviolet spectrum has also been accomplished. Typically, the gain medium is ionized by an auxiliary ionization source and the electric field provides the energy to maintain the discharge in a self-sustaining mode. Laser systems having gain media including halide and rare-gas elements have the potential for operating with high efficiency with proper excitation. The utilization of electron beam pumping techniques has produced optical emissions having a wavelength of 0.410 microns from an argon/krypton/fluorine gas mixture with a pressure of nine atmospheres.
Prior art devices for producing laser beams from gain media including halide and rare-gas elements have suffered from several serious deficiencies. For the electron beam techniques, the size and complexity of the electron beam system as well as the tendency of the foil window to fail have prevented the development of these systems for practical applications requiring compact, lightweight lasers which can operate at high repetition rates. Additionally, the operation at high pressures have been precluded by the fragileness of the metal foil. On the other hand, while the direct discharge technique is more readily adapted to practical devices, it is severely limited by the tendency of the discharge for form arcs rather than to remain diffuse as required to efficiently extract optical energy from a gain media. This is particularly true for high pressure operations.